llama.cpp moves too quickly to be added as a stable package. Instead, you can get it directly from AUR: https://aur.archlinux.org/packages?O=0&K=llama.cpp
There are packages for Vulkan, ROCm and CUDA. They all work.
There are packages for Vulkan, ROCm and CUDA. They all work.
Edit: Or perhaps put differently: If ollama includes a copy of llama.cpp and has a non-AUR package, why can't there be a non-AUR package that's just llama.cpp without ollama?